Regardless of the digitization of technology and the workplace, use of paper is growing on an annual basis. Global production in the pulp, paper and publishing sector is expected to increase by 77% from 1995 to 2020. A large majority of pages printed both at home and in the workplace are disposed of, either as trash or by recycling, the average lifespan of a print being less than 1 day. Thus, the amount of waste is enormous; about 700 pounds of paper are consumed by the average American every year. Although paper is not considered an expensive commodity, the economic impact of the sheer volume is tremendous; this is estimated at about 10000 pages per year per office employee.
Erasable paper and supporting printing systems provide an interesting alternative to standard paper. An erasable paper and supporting printing system allows printing information on either treated or plain paper with the capacity to erase the information from the paper, or for the information to disappear from the paper after a certain period, allowing the paper to be reused.
Generally erasable paper will be a paper treated with an overcoat which can undergo a photochromic, thermochromic or other transition which prints and erases when using specifically designed print systems. Photochromic papers print when irradiated at a specific wavelength, often in the UV range and erased when exposed to a different wavelength. A thermochromic paper would be printed by various methods including irradiation, mild heat, chemicals, etc. and erased when heated above a threshold temperature, typically above 100° C.
Many examples exist describing single use and multiple use of photochromic papers (e.g. XEROX in US 2011/0037803). RICOH and their subsidiaries disclose having designed a thermochromic paper wherein erasing is done either by heat or light (e.g. U.S. Pat. No. 7,732,373). TOSHIBA discloses having developed a heat sensitive thermoplastic toner. Wherein upon heating the thermoplastic toner particles flow forming a thin transparent layer (e.g. US 2011/0165507). CASIO describes developing a negatively charged toner that can be electrostatically removed from the paper using a device designed for doing so (e.g. US 2012/0264044). Hewlett Packard describes developing a print system and ink that is erasable using electrical erasing (e.g. U.S. Pat. No. 6,544,601).
Older methods include the use of solvent to remove toners, (e.g. IBM U.S. Pat. No. 4,413,266 and Cannon U.S. Pat. No. 6,379,001): The solvents may be organic, inorganic or mixtures and demand the use of soluble inks.
A problem with the above methods is that they require special printers, special toner or ink, leave markings on the paper or damage the paper, so that the paper can only be used a few times (e.g. 2-4).
In an article by David Ricardo Leal-Ayala, J. M. Allwood, M. Schmidt, and I. Alexeev, “Toner-print removal from paper by long and ultrashort pulsed lasers” (Proceedings of the Royal Society A: Mathematical Physical and Engineering Sciences, vol. 468. pp. 2272-2293. They disclose attempts to remove laser print toner from standard paper by using ultrafast long pulsed lasers to irradiate the toner particles and remove them from the paper. The process requires use of specific wavelengths with short pulse duration to minimize damage to the paper. They disclose having some success in vaporizing most of the toner on standard paper, so that the paper may be used up to two or three times.
In summary the current state of the art technology is essentially limited to:
1. Specifically designed paper, not compatible with standard printer systems
2. Specifically designed inks and toners that may or may not require special printers.
3. Specifically designed printers, usually with slower print times and higher costs per page than typical home and business printers
4. Paper often suffers discoloration after erasing.
5. Paper often suffers from deformation after erasing, typically curling, Paper is generally only reusable a limited number of times (e.g. less than ten).
6. Systems force offices to maintain two types of printing systems, one for storage and one which is erasable.